In forumdisplay template, remove $vbphrase[threads_in_forum]
Code:
<!-- / controls above thread list -->
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center" style="border-bottom-width:0px">
<tr>
<td class="tcat" width="100%">$vbphrase[threads_in_forum]<span class="normal"> : $foruminfo[title]</span></td>
<td class="vbmenu_control" id="forumtools" nowrap="nowrap"><a href="$show[nojs_link]#goto_forumtools" rel="nofollow">$vbphrase[forum_tools]</a> <script type="text/javascript"> vbmenu_register("forumtools"); </script></td>